Slide transport device

ABSTRACT

A device for transporting slides in a horizontal plane to be projected by a slide projector.

United States Patent Costanza et al.

SLIDE TRANSPORT DEVICE Inventors: Carl C. C0stanza,Chicago, 111.;

Walter W. Weber, Des Plaines, Ill.; Frank W. Betlejewski, Chicago, 11].;Richard Frystak, Park Ridge, Ill.

Assignee: Bell & Howell Company, Chicago,

Filed: July 6, 1971 Appl, No.: 160,020

Related U.S. Application Data Division of Ser. No. 860,384, Sept. 23,1969, Pat. No. 3,659,934.

U.S. Cl 353/112, 353/117, 353/21 Int. Cl. G03b 23/06 Field of Search353/103-117 1 Nov. 20, 1973 [56] References Cited UNITED STATES PATENTS3,002,426 10/1961 McCabe 353/112 3,574,454 4/1971 Deeg 353/113 FOREIGNPATENTS OR APPLICATIONS 747,066 1/1944 Germany 353/117 1 1,127,3319/1962 Great Britain 353/DIG. 1

Primary Examiner-Louis R. Prince Assistant Examiner-A. J. MirabitoAttorney.lohn L. Cline [5 7 ABSTRACT A device for transporting slides ina horizontal plane to be projected by a slide projector.

18 Claims, 9 Drawing Figures 'PATENIED NOV 20 I975 SHEET 6 OF 5 SLIDETRANSPORT DEVICE CROSS-REFERENCES TO RELATED APPLICATIONS This is adivision of application Ser. No. 860,3 84 filed Sept. 23, 1969 now U.-S.Pat. No. 3,659,934.

This application relates to the inventions in copending application Ser.Nos. 735,730, filed June 10, 1968; 860,336; 860,385; 860,856; 860,857;and 860,858; all filed Sept. 19, 1969.

BACKGROUND OF THE INVENTION This invention relates generally to thefield of slide projectors. More specifically, it relates to slidehandling apparatus finding particular utility in the slide projectordescribed in co-pending application Ser. No. 735,730, 'filed June 10,1968.

That projector overcomes many prior art problems by presenting slides toprojection apparatus in a horizontal plane. Horizontal orientationprovides a convenient means for effecting pre-viewing of a slide beforeactual projection. The complexity of the requisite apparatus ismaterially reduced and great increases in reliability manifestthemselves. However, the development of novel slide transport apparatuswas needed to utilize the horizontal presentation approach. Thisinvention responds to that need and encompasses a slide transport systemthat simply, economically and with a high degree of reliability presentsa continuous supply of slides in a horizontal plane to operativestations of a slide projector.

The ability to reverse the normal projection sequence so a previouslyviewed slide may be re-projected without completely re-cycling'a givensupply of slides, obviously adds a large measure of utility to a slideprojector. Inadvertent cycling, a forgotten thought, or reprojection forcloser examination, among many others, provide reasons for wishing toreverse the normal sequencing of a slide supply. Horizontal projectiondemanded a novel transport system to accomplish the above task and thisinvention responds to that demand.

Additionally this invention comprehends apparatus that allows the sameoperative station on the projector to be used for slide entry into andexit from the projector. While facilitating the reverse mode ofoperation of the projector, this feature also minimizes the spacerequirements and esthetic considerations are concurrently enhanced.

Also a part of the entry-exit station apparatus is a novel mechanism forreleasing an element from holding means. This feature enhances theremoval of a projected series of slides from the slide projector toallow insertion of a second supply.

SUMMARY OF THE INVENTION This invention has been developed to transportslides through four operative stations: entry, pre-viewing, projection,post-projection and finally returning to the entry station which servesas an exit station after the foregoing path has been traversed, thus itscharacterization previously as an entry-exit station. However, as willbecome more apparent herein there could be fewer or more operativestations if so desired. A platen with apertures corresponding to theabove operative stations is provided. only the aperture at theentry-exit station need be large enough to allow the passage of a slide.Horizontal transport surfaces at two levels are Leaving the projectionstation the slide travels down a a ramp or inclined plane to the lowerlevel transport surface prior to positioning at the post-projectionstation. Continuing on the lower level the slide again reaches theentry-exit station, being located on the lower level the slide exitsfrom the projection apparatus through the exit aperture.

' A pair of spring biased arms overlying the exit aperture prevent aslide placed thereon when entering the projector from dropping throughthe aperture. The arms are so constructed that the slide passes underthem when on the lower transport level and may then exit from theprojection apparatus through that aperture. A plate-like upper surfaceoverlying the path from the post-projection station to the arms at theentry-exit station provides a transport surface for a new slide restingon the arms when the normal sequence of operation reversed. Thereby thenew slide will not fall to the lower surface during the reverse mode ofoperation, which prevents its exit during the next normal cycle.

Via slots in a housing overlying the projector, a supply cartridge ofslides is slid horizontally into position over the spring urged arms.Underlying the exit aperture a vertical receiving chamber with aplatform slideably located therein provides apparatus for collecting theviewed slides. After the slide supply is exhausted and slides arecontained within the chamber, merely lifting the platform pushes theslides between and through the spring urged arms into the supplycartridge. Detent means hold the platform in its upper position where itremains until the slide supply cartridge is slid far enough so theplatform no longer supports the slides. Inclined plane grooves formed inthe upper surface of the platform cooperate with a like number of tabs,any number will suffice, extending downwardly from the supply cartridge.As the tabs are slid within the grooves ultimately a point is reachedwhere the force applied by the tabs to the platform is sufficient toforce it out of engagement with the detents whereupon it drops down intothe receiving chamber.

BRIEF DESCRIPTION OF THE DRAWINGS The features of the invention willbecome more apparent in the following detailed description and drawingswherein:

FIG. 1 is a top view of the transport apparatus and showing two slidesin position thereon.

FIG. 2 is a perspective view of the platen which comprises the transportsurfaces.

FIG. 3 is a perspective view of a slide beginning-to fall through theexit aperture into the receiving chamber.

FIG. 4 is a perspective view of the drive plate which moves the slidesthrough the projector.

FIG. 5 is a perspective view of the retaining means.

FIG. 6 is a cross-sectional view taken along line 6-6 in FIG. 1 of theprojector more fully assembled than in FIG. 1.

FIG. 7 is a portion of FIG. 6 in a different operative condition.

FIG. 8 is a view of one side of the receiving chamber.

FIG. 9 is a perspective view of the slide ejection apparatus in itsuppermost position.

Referring to FIG. 2 there is seen the platen 10 of the apparatus. Fourapertures 12, 14, 16, 18 are cut in the platen, and correspond to theoperative stations of the slide projector: entry-exit, pre-viewing,projection, and post-projection respectively. A retaining means 28, moredetailed in FIG. 5, is positioned above the exit aperture 12 to preventa supply of slides placed on its upper surfaces 34 from dropping throughthe exit aperture 12.

The retaining means 28 consists of two retaining arms 32 having a flatupper-surface 34 and a bevelled under-surface 37 positioned in sockets36 to permit rotational movement thereof and a spring 30 which urgeselements 32 towards one another. The spring 30 urges the arms 32together to the point that a slide may be placed in contact with bothupper surfaces 34. However, the retaining means must be constructed toallow sufficient separation of the retaining arms 32 to permit passageof a slide between them.

The pre-viewing aperture 14 located substantially 90 from the exitaperture permits the operator to view a slide prior to projection asmore fully set out in copending application Ser. No. 735,750.

The projection aperture 16, positioned substantially 90 from thepre-viewing aperture, permits projection of a slide on a conventionalviewing screen. As best seen in FIG. 6, a light source 52 underneathaperture 16, a projection mirror and focusing lens shown generally, butnot illustrated in detail, at 50 above the projection aperture 16 effectthe projection of a slide placed over the projection aperture 16. Asuitable mirror and focusing lens are described in co-pendingapplication Ser. No. 860,858. Spill light from light source 52illuminates apertures 14 and 18.

Post-projection viewing aperture 18 allows the operator to determinewhich slide has last been projected in a manner similar to that at thepre-viewing aperture 14.

The realization that the slides to be viewed are placed above theretaining device 28, and then sequentially are transported to thepre-viewing aperture 14, the projection aperture 16, the post-projectionaperture 18, and finally through the exit aperture 12 will aid in theunderstanding of the following description.

The platen 10 has an annular outer raised portion 20, inner raisedsurface 22, inclined plane surfaces 24, a plate-like surface 25, aholding plate surface 26 shown partly broken away, and a lower surface23. The above described surfaces define the areas on which a slidetravels from retaining means 28 to exit aperture 12.

FIG. 4 illustrates the drive plate 40 utilized to move slides along thetransport surfaces 20, 22, 24, 23, 26. The drive plate 40 embodies aflat generally circular plate, four receiving apertures 42, pushing tabs46 and gear teeth 44 which exist about the entire circumference.

As seen in FIG. 6, the drive plate 40 is rotatably fastened above theplaten 10 by a conventional fastener 72. It should be pointed out thatwhile FIG. 6 is taken along lines 66 of FIG. 1, FIG. 6 shows theapparatus in a more fully assembled condition than FIG. 1 for reasons ofclarity. In FIG. 1 the drive plate 40 is partially illustrated and itcan be seen that gear teeth 44 mesh with gears indicated generally at 8.

A motor, not shown, drives the gears 8 which in turn drive gear teeth 44and the drive plate 40 is thusly rotated relative to base platen 10. Themotor preferrably is adapted to be driven in forward and reversedirections, thus permitting bi-rotational movement of the drive plate40.

The tabs 46 are spaced to correspond to the gaps between inclined planeareas 24 and at least one tab on each side of each receiving aperture 42extends far enough to contact the edge of a transparency on the lowersurface 23 of the platen 10.

The edges 45 of the receiving apertures 42 are bevelled to facilitateentry of a slide. The receiving apertures 42 are spaced substantiallyfrom one another and coincide with the apertures l2, 14, 16, 18 in theplaten 10 when they are in overlying relationship.

As best seen in FIG. 6, slides 60 are supplied to the transportapparatus from a supply cartridge 54 positioned over the upper surfaces34 of retaining elements 32 by insertion into a housing 38 whichoverlies drive plate 40. The cartridge 54 is slid horizontally intoposition with its flanges 41 (FIG. 7) cooperating with grooves 39. Thesupply cartridge is more fully described in co-pending application Ser.No. 860,856.

Beneath the platen l0 and coincidental with the exit aperture 12, areceiving chamber 62 collects the slides 60 after projection. The shapeof the supply cartridge 54 and the receiving chamber 62, as well as theshape of apertures 42, 12, 14, 16, 18 are slightly larger than andconform generally to the shape of the slides, in this case approximatelysquare. However, it should be apparent that the shapes of the aperturesare relatively immaterial so long as they permit entry of a slide andtransferral of a slide from one to the other.

The device is ready for operation when the centers of slides 60 in thesupply cartridge, an aperture 42 in the driving plate, the exit aperture12 in the platen and the receiving chamber 62 are substantiallycoincidentally positioned. As seen in FIG. 6, a slide will begravitationally urged against the upper surface 34 of retaining elements32 within a receiving aperture 42 of the drive plate 40.

Activation of drive means 8 to produce 90 of counterclockwise rotation(FIG. 1) of drive plate 40 causes a single slide to be urged by the tabs46 and the edges 45 of the receiving aperture 42 along the surfaces 20,22 of the platen until the center of the slide substantially coincideswith the center of the pre-viewing aperture 14.

A metering device (not shown) may be added to ensure that only a singleslide, regardless of thickness, will be carried by the receivingaperture 42.

A second 90 counter-clockwise rotation of the drive plate 40 causes theslide to move along surfaces 20, 22 to a point where its center issubstantially coincident with that of projection aperture 16. FIG. 1illustrates a slide 63 supported by surfaces 20, 22 and moved by tabs 46at a point between the pre-viewing aperture 14 and the projectingaperture 16.

A third 90 counter-clockwise rotation of the drive plate 40 will forcethe slide down inclined plane surfaces 24, under the holding plate 26and the plate-like portion 25 of the platen l0 and onto the lowersurface 23 of the platen to a point where its center is substantiallycoincident with that of the post-projection viewing aperture 18. Theslide 61 in FIG. 1 is illustrated as it travels down the inclined planesurfaces 24, note that the tabs 46 travel between the inclined planesurfaces 24.

A fourth 90 counter-clockwise rotation of the drive plate 40 will causeone of the pusher tabs 46 to urge the slide along the lower surface 23of the platen under the retaining elements 32 until the slide drops intothe receiving chamber 62 through the exit aperture 12. FIG. 3 shows aslide 65 about to fall into the receiving chamber. For reasons ofclarity, illustration of the platen 10 and the retaining mechanism 28has been partially omitted from FIG. 3.

Thus a slide enters the transport mechanism, completes a 360 paththrough the operative stations and is ejected from the transportmechanism.

It should be apparent that as the drive plate 40 is rotated through each90 segment, a new slide will enter a receiving aperture 42 presented tothe supply cartridge 54. Therefore the presentation of slides to theprojection aperture 16 will be continuous until the slides 60 areexhausted from the supply cartridge 54.

An important feature of this invention is the capability to reverse thenormal operating sequence and reproject a slide that has been projectedand cycled to the post-projection viewing aperture 18.

The most frequent operating condition of the projector occurs after thedrive plate 40 has been rotated counter-clockwise at least 360 andtherefore all four receiving apertures 42 contain a slide coincidentwith the apertures 12, 14, l6, 18 of the base plate 10. Should it bedesired to re-project the slide coincident with the post-projectionaperture 18, the drive plate 40 need merely be rotated 90 in a clockwisedirection. The slide formerly at the post-projection viewing aperture 18will move up the inclined plane surfaces 24 to a position coincidentwith the projection aperture 16. The slide formerly at the projectionaperture 16 will move along surfaces 20, 22 to a point coincident withthe pre-viewing aperture 14. The slide formerly at the previewingaperture 14 will move along surfaces 20, 22 and onto the upper surfaces34 of the retaining elements 32 to a point coincident with the exitaperture 12. The slide formerly resting on the upper surface 34 of theretaining elements 32 will move along the holding plate surface 26 andthe plate-like surface 25 to a point coincident with the post-projectionviewing aperture 18, but above the lower surface 23 of the platen 10.

Because a second consecutive clockwise rotation would force the slideresting on surfaces 25, 26 to drop onto the inclined plane surface 24and be transported to the projection aperture 16, the projection of aslide out of sequence from the order the slides 60 are put into thesupply cartridge 54 would result.

To avoid non-sequential projection, it is necessary to limit reversal ofthe drive plate 40 to a single 90 clockwise rotation at any one time. Adevice for accomplishing that end is the subject of co-pendingapplication Ser. No. 860,336.

Turning to FIG. 6, it is seen that a loading platform 68 and a spring 64are contained within the receiving chamber 62. The loading platform 68nestles slideably within the receiving chamber 62. The receiving chamber62 defines a longitudinally extending orfice with substantially the samecross-sectional shape as that of the slides. The particular shape of thereceiving chamber 62 is unimportant as long as it permits slides toenter freely and be positioned in a horizontal plane when their fallceases. The loading platform 68 is free from the spring 64, the functionof the spring 64 merely to position the loading platform near the exitaperture 12 to reduce the distance a slide must fall to be supported bythe platform.

As best illustrated in FIG. 3, a handle 70, attached to the loadingplatform 68, extends through a slot 67 in the receiving chamber 62. Thehandle may be utilized to manually effect vertical movement of theloading platform 68.

After a given supply of slides has been exhausted and they are locatedin the receiving chamber 62, the slides must be ejected from thereceiving chamber 62. The cooperation of the slideable loading platform68 and the retaining means 28 rapidly accomplishes the desiredejectment.

Best understood by comparing FIGS. 6, 7 and 9, when the loading platform68 is raised by the handle 70 the slides are urged against the bevelledsurface 37 (FIG. 5) of the retaining arms 32 causing them to spreadapart and permit passage of the slides. FIG. 7

illustrates the ejection process near its completion. When the platform68 reaches its uppermost position (FIG. 9) all of the slides arecontained with the slide cartridge 54 and the cartridge may be removedby sliding in a leftwardly direction. A detent 80 maintains the platformin its uppermost position until the slides are moved far enough thatsupport from the platform 68 is unnecessary. If the platform 68 werelowered before it ceased to support the slides, they would drop intoengagement with the upper surface 34 of the retaining arms as shown bythe upper group of slides in FIG. 6 and the lowermost slides would jamwith the drive plate 40 and the housing 38 if the leftward sliding (FIG.9) were continued.

Inclined plane surfaces 75, on the upper surface of the platform 68cooperate with tabs 74, 74 projecting from the upper edge of thecartridge 54 to release the platform from the detent when the cartridgehas been slid leftwardly enough to permit release of the platform 68. Asthe cartridge 54 slides leftwardly, the tabs 74, 74 exert anincreasingly greater downward force on the platform until the detent 80is forced beneath the upper surface of the platen 10. whereupon theplatform falls into the receiving chamber 62 and the entry-exit stationwill be able to accommodate another supply cartridge 54 when the firstis removed.

It should be apparent that additional detents could be added if sodesired. Furthermore although two tabs 74, 74 and associated grooves 75,75 have been described only one set is absolutely necessary and ofcourse, more could be added. It should again be noted that a suitablesupply cartridge 54 has been made the subject of copending applicationSer. No. 860,856.

Another feature of this invention is illustrated in FIG. 8. When slidesare first received after processing they are not contained within asupply cartridge 54. To allow the photographer to view the new slidesbefore putting them into a supply cartridge 54, means (not shown) areprovided at the previewing aperture 14 to allow insertion into the slidetransport apparatus by hand.

It then becomes necessary to know how many slides have been cycled intothe receiving chamber 62 so that no more than can easily be held by thesupply cartridge 54 are placed therein.

To that end slots 66 have been cut into a wall of the receiving chamber.Spill light from the light source 52 illuminates the slots 66 and thusthe level of the slides in the receiving chamber may easily bedetermined by appropriate markings or with reference to the top of theslot. Colored cellophane or the like may be placed over the slot 66 toreduce glare.

That the particular shape of the slide and thus the correspondingapertures could easily be changed from what has been described forillustration purposes should be apparent.

Furthermore, the deletion of the pre-viewing station and/or thepost-projection station could easily be effected with correspondingmodifications.

Also the addition of operative stations would not substantially affectthe invention.

Thus apparatus which provides a convenient means for handling slideswithin a slide projector has been described. It should be obvious thatmany modifications and alterations of the embodiments above-describedmay be made without departing from the spirit and scope of the inventionas set forth in the appended claims.

Having thus described the invention, what is claimed 1. In a slideprojector the combination comprising:

an entry-exit station for receiving slides at a first level and ejectingsaid slides at a second level;

a projection station including illumination means;

and

transport means for continuously transporting horizontally orientedslides along a curved path from said first level of said entry-exitstation to said projection station and thereafter to said second levelof said entry-exit station to cause the projected slides to be ejectedfrom said transport means.

2. The combination set forth in claim 1 further comprising:

a previewing station; and

wherein said transport means includes means for continuouslytransporting a supply of slides received at said first level to saidpreviewing station, thereafter to said projection station and thereafterto said second level of said entry-exit station.

3. The combination set forth in claim 2 further comprising:

a post-projection station;

said stations being substantially equi-spaced from each other anddisposed on the circumference of a circle; and

wherein said transport means includes both means for continuouslytransporting a supply of slides received at said first level to saidpreviewing station, thereafter to said projection station, thereafter tosaid post-projection station and thereafter to said second level of saidentry-exit station, and also means for reversing the above transportpath during which a slide positioned at said first level of saidentry-exit station is transported to a position above saidpost-projection station.

4. A slide projector comprising:

an entry-exit station for receiving a horizontally disposed slide at anupper level and ejecting slides from the transport assembly of saidprojector at a lower level;

a previewing station;

a projection station including a light source;

a post-projection station;

said stations being substantially equi-spaced from one another on acircular slide travel path;

a bi-level platen having slide transport surfaces at said upper andlower levels, said transport surfaces being disposed on said circulartravel path;

drive means overlying said platen for continuously transporting saidslides received at said upper level along said path sequentially throughsaid previewing, projection post-projection and entry-exit stations,said transported slides being returned thereby to said lower level ofsaid entry-exit station; and means for reversing said drive means. 5. Ina slide projector the combination comprising: an entry station includingmeans for supporting a stack of horizontally oriented slides at an upperlevel; a projection station; an exit station including a chamber havingan open end disposed at a lower level for receiving projected slides;and transport means for transporting slides, one at a time, from saidupper level at said entry station to said open end of said chamber atsaid lower level; said transport means being operable in a forwarddirection for transporting slides one at a time from said upper level atsaid entry station to said open end of said chamber and operable in areverse direction for simultaneously returning a slide to saidprojection station for reprojection and transporting a slide from saidupper level at said entry station in a reverse direction in a path abovesaid lower level. 6. The combination set forth in claim 5 wherein saidtransport means comprises a platen having transport surfaces forsupporting said slides and an apertured disc rotatably mounted in saidprojector for moving said slides along said transport surfaces.

7. In a slide projector having an entry station for receiving a stack ofhorizontally oriented slides, a projection station and an exit station,the transport mechanism comprising:

a rotatable disc having apertures for receiving slides at said entrystation and for transporting said slides between said stations; and

a platen underlying said disc having transport sur faces formed thereinfor supporting slides as they are moved by said disc, said transportsurfaces communicating with said entry station at an upper level andwith said exit station at a lower level.

8. The combination set forth in claim 7 further including transportsurfaces that communicate with said entry station at said upper leveland overlie at least a portion of said lower level transport surfaces.

9. An apparatus for projecting slides one at a time from a verticalstack of horizontally oriented slides having an entry station located ina first plane, an exit station located in a second plane, a projectionstation and a transport means for conveying said slides between saidstations, the improvement comprising:

a post projection station intermediate the projection and exit stations;

a first support means located between a first side of said entry stationand said projection station wherein said transport means is adapted toremove a first slide from said stack and to convey said first slidealong said first support means in a forward direction from said .entrystation to said projection station;

a second support means located between said projection station and saidpost projection station wherein said transport means is adapted toconvey said slide along said second support means from said projectionstation to said post projection station; and

a third support means located between said post projection station andsaid exit station wherein said transport :means is adapted to conveysaid slide along said third support means to said exit station.

10. The apparatus of claim 9 wherein said transport means is furtheradapted to move in a reverse direction and convey said first slide alongsaid second support means from said post projection station back to saidprojection station.

11. The apparatus of claim 9 further comprising a fourth support meansconnected to a second side of said'entry station and wherein saidtransport means is adapted to move in a reverse direction andsimultaneously convey said first slide along said second guide meansfrom said post projection station back to said projection station whileremoving a second slide from said stack and conveying said second slidealong said fourth support means.

12. In a slide projector including an entry station, a projectionstation and an exit station, a transport surface between said stations,and transport means for sliding a slide along said transport surfacebetween said stations the improvement comprising:

means for supporting a slide at a first level at said entry station forengagement with said transport means;

means at said exit station for disengaging a slide from said transportmeans at a second level;

said transport surface extending in a forward direction from said firstlevel to said second level; and

an additional transport surface extending in a reverse direction fromsaid first level at said entry station and disposed above said secondlevel, whereby upon reversal of said transport means a slide may beprojected and a slide positioned at said entry station will betransported along said additional transport surface.

13. A slide projector capable of reprojecting a slide comprising:

an entry station including means for supporting the lowermost of a stackof horizontally oriented slides at a first level;

a projection station spaced from said entry station;

first transport surfaces extending in a forward direction from saidsupporting means through said projection station to a point oftermination at a second level lower thansaid first level, saidtermination being at an exit station;

additional transport surfaces extending in a reverse direction from saidsupporting means;

rotary transport means for moving horizontally oriented slides on saidtransport surfaces along a substantially circular path; and

means for selectively driving said transport means in forward andreverse directions.

14. In a slide projector including substantially horizontal transportsurfaces; rotary transport means for sliding a substantiallyhorizontally oriented slide on said surfaces from an entry station in aforward direction through a projection station to an exit station alonga substantially circular path, said exit station being a termination ofsaid-surfaces whereby a slide drops gravitationally therefrom into areceiving chamber the improvement comprising:

means for supporting the lowermost slide of said supply in said entrystation at a first vertical level;

substantially horizontal transport surfaces that extend in a forwarddirection from said entry station through said projection station to atermination at said exit station disposed at a second vertical levellower than said first level; and

additional substantially horizontal transport surfaces extending in areverse direction from said entry station that are disposed at saidfirst level and overlie a portion of said transport surfaces terminatingat said second level whereby upon reversal of said rotary transportmeans the last projected slide may be reprojected at said projectionstation and the lowermost slide of said supply may be transported insaid reverse direction along said additional transport surfaces.

15. A slide projector for projecting and reprojecting slides from astack supply comprising:

an entry station adapted to support the lowermost slide in said stack ina first plane;

a projection station spaced from said entry station;

first transport surfaces disposed in said first plane extending betweensaid entry station and said projection station;

a post projection station spaced from said projection station disposedin second plane lower than said first plane;

second transport surfaces extending between said projection station andsaid post projection station;

an exit station comprising a chamber with an open end disposed in saidsecond plane and underlying said entry station;

third transport surfaces disposed in said second plane extending betweensaid post projection station and said open end of said chamber;

fourth transport surfaces disposed in said first plane extending betweensaid entry station and a point above said post projection station; and

slide transport means for receiving slides one at a time at said entrystation and for transporting said slides between said stations whereby aslide located at said post projection station may be returned to saidprojection station along said third transport surfaces for reprojectionand simultaneously therewith the lowermost slide in said stack may betransported along said fourth transport surfaces to a position overlyingsaid post projection station.

16. A slide projector for projecting slides one at a time from a stackof horizontally oriented slides and for permitting projection of a slidethat comprises:

an entry station including means for receiving a stack of horizontallyoriented slides and means for positioning the lowermost slide in saidstack at an upper level;

a projection station including means for projecting a horizontallyoriented slide;

an exit station including means for receiving a projected slide at alower level;

said stations being equi-spaced from an axis;

a carrier rotatable in forward and reverse directions about said axisincluding means for engaging slides when said carrier is rotated ineither direction to move said slides between said stations; and

transport surfaces underlying said carrier for supporting slides as theyare moved by said carrier including a first position that communicateswith one side of said entry station at said upper level, passes throughsaid projection station and terminates in said exit station at saidlower level and a second portion that communicates with the other sideof said entry station at said first level.

17. A slide projector capable of reprojecting a slide after it has beenprojected and a second slide has been cycled into a projection positionthat comprises:

a projection station including means for projecting a horizontallyoriented slide and means for supporting a horizontally oriented slide ata first level; and

an exit station spaced from said projection station including means forremoving a slide at a second level from the transport means of saidprojector;

said transport means including a transport surface extending along acurved travel path from said first level at said projection station tosaid second level at said exit station and motive means for movingslidesalong said transport surface, whereby a slide positioned betweensaid projection station and said exit station may be reprojected byreversing said motive means.

18. In a slide projector the combination comprising;

an entry station including means for supporting a stack of horizontallyoriented slides at an upper level;

a projection station;

an exit station including a chamber having an open end disposed at alower level for receiving projected slides; and

transport means for transporting slides one at a time along a curvedtravel path from said upper level at said entry station to said open endof said chamber.

1. In a slide projector the combination comprising: an entry-exitstation for receiving slides at a first level and ejecting said slidesat a second level; a projection station including illumination means;and transport means for continuously transporting horizontally orientedslides along a curved path from said first level of said entry-exitstation to said projection station and thereafter to said second levelof said entry-exit station to cause the projected slides to be ejectedfrom said transport means.
 2. The combination set forth in claim 1further comprising: a previewing station; and wherein said transportmeans includes means for continuously transporting a supply of slidesreceived at said first level to said previewing station, thereafter tosaid projection station and thereafter to said second level of saidentry-exit station.
 3. The combination set forth in claim 2 furthercomprising: a post-projection station; said stations being substantiallyequi-spaced from each other and disposed on the circumference of acircle; and wherein said transport means includes both means forcontinuously transporting a supply of slides received at said firstlevel to said previewing station, thereafter to said projection station,thereafter to said post-projection station and thereafter to said secondlevel of said entry-exit station, and also means for reversing the abovetransport path during which a slide positioned at said first level ofsaid entry-exit station is transpoRted to a position above saidpost-projection station.
 4. A slide projector comprising: an entry-exitstation for receiving a horizontally disposed slide at an upper leveland ejecting slides from the transport assembly of said projector at alower level; a previewing station; a projection station including alight source; a post-projection station; said stations beingsubstantially equi-spaced from one another on a circular slide travelpath; a bi-level platen having slide transport surfaces at said upperand lower levels, said transport surfaces being disposed on saidcircular travel path; drive means overlying said platen for continuouslytransporting said slides received at said upper level along said pathsequentially through said previewing, projection post-projection andentry-exit stations, said transported slides being returned thereby tosaid lower level of said entry-exit station; and means for reversingsaid drive means.
 5. In a slide projector the combination comprising: anentry station including means for supporting a stack of horizontallyoriented slides at an upper level; a projection station; an exit stationincluding a chamber having an open end disposed at a lower level forreceiving projected slides; and transport means for transporting slides,one at a time, from said upper level at said entry station to said openend of said chamber at said lower level; said transport means beingoperable in a forward direction for transporting slides one at a timefrom said upper level at said entry station to said open end of saidchamber and operable in a reverse direction for simultaneously returninga slide to said projection station for reprojection and transporting aslide from said upper level at said entry station in a reverse directionin a path above said lower level.
 6. The combination set forth in claim5 wherein said transport means comprises a platen having transportsurfaces for supporting said slides and an apertured disc rotatablymounted in said projector for moving said slides along said transportsurfaces.
 7. In a slide projector having an entry station for receivinga stack of horizontally oriented slides, a projection station and anexit station, the transport mechanism comprising: a rotatable dischaving apertures for receiving slides at said entry station and fortransporting said slides between said stations; and a platen underlyingsaid disc having transport surfaces formed therein for supporting slidesas they are moved by said disc, said transport surfaces communicatingwith said entry station at an upper level and with said exit station ata lower level.
 8. The combination set forth in claim 7 further includingtransport surfaces that communicate with said entry station at saidupper level and overlie at least a portion of said lower level transportsurfaces.
 9. An apparatus for projecting slides one at a time from avertical stack of horizontally oriented slides having an entry stationlocated in a first plane, an exit station located in a second plane, aprojection station and a transport means for conveying said slidesbetween said stations, the improvement comprising: a post projectionstation intermediate the projection and exit stations; a first supportmeans located between a first side of said entry station and saidprojection station wherein said transport means is adapted to remove afirst slide from said stack and to convey said first slide along saidfirst support means in a forward direction from said entry station tosaid projection station; a second support means located between saidprojection station and said post projection station wherein saidtransport means is adapted to convey said slide along said secondsupport means from said projection station to said post projectionstation; and a third support means located between said post projectionstation and said exit station wherein said transport means is adapTed toconvey said slide along said third support means to said exit station.10. The apparatus of claim 9 wherein said transport means is furtheradapted to move in a reverse direction and convey said first slide alongsaid second support means from said post projection station back to saidprojection station.
 11. The apparatus of claim 9 further comprising afourth support means connected to a second side of said entry stationand wherein said transport means is adapted to move in a reversedirection and simultaneously convey said first slide along said secondguide means from said post projection station back to said projectionstation while removing a second slide from said stack and conveying saidsecond slide along said fourth support means.
 12. In a slide projectorincluding an entry station, a projection station and an exit station, atransport surface between said stations, and transport means for slidinga slide along said transport surface between said stations theimprovement comprising: means for supporting a slide at a first level atsaid entry station for engagement with said transport means; means atsaid exit station for disengaging a slide from said transport means at asecond level; said transport surface extending in a forward directionfrom said first level to said second level; and an additional transportsurface extending in a reverse direction from said first level at saidentry station and disposed above said second level, whereby uponreversal of said transport means a slide may be projected and a slidepositioned at said entry station will be transported along saidadditional transport surface.
 13. A slide projector capable ofreprojecting a slide comprising: an entry station including means forsupporting the lowermost of a stack of horizontally oriented slides at afirst level; a projection station spaced from said entry station; firsttransport surfaces extending in a forward direction from said supportingmeans through said projection station to a point of termination at asecond level lower than said first level, said termination being at anexit station; additional transport surfaces extending in a reversedirection from said supporting means; rotary transport means for movinghorizontally oriented slides on said transport surfaces along asubstantially circular path; and means for selectively driving saidtransport means in forward and reverse directions.
 14. In a slideprojector including substantially horizontal transport surfaces; rotarytransport means for sliding a substantially horizontally oriented slideon said surfaces from an entry station in a forward direction through aprojection station to an exit station along a substantially circularpath, said exit station being a termination of said surfaces whereby aslide drops gravitationally therefrom into a receiving chamber theimprovement comprising: means for supporting the lowermost slide of saidsupply in said entry station at a first vertical level; substantiallyhorizontal transport surfaces that extend in a forward direction fromsaid entry station through said projection station to a termination atsaid exit station disposed at a second vertical level lower than saidfirst level; and additional substantially horizontal transport surfacesextending in a reverse direction from said entry station that aredisposed at said first level and overlie a portion of said transportsurfaces terminating at said second level whereby upon reversal of saidrotary transport means the last projected slide may be reprojected atsaid projection station and the lowermost slide of said supply may betransported in said reverse direction along said additional transportsurfaces.
 15. A slide projector for projecting and reprojecting slidesfrom a stack supply comprising: an entry station adapted to support thelowermost slide in said stack in a first plane; a projection stationspaced from said entry sTation; first transport surfaces disposed insaid first plane extending between said entry station and saidprojection station; a post projection station spaced from saidprojection station disposed in second plane lower than said first plane;second transport surfaces extending between said projection station andsaid post projection station; an exit station comprising a chamber withan open end disposed in said second plane and underlying said entrystation; third transport surfaces disposed in said second planeextending between said post projection station and said open end of saidchamber; fourth transport surfaces disposed in said first planeextending between said entry station and a point above said postprojection station; and slide transport means for receiving slides oneat a time at said entry station and for transporting said slides betweensaid stations whereby a slide located at said post projection stationmay be returned to said projection station along said third transportsurfaces for reprojection and simultaneously therewith the lowermostslide in said stack may be transported along said fourth transportsurfaces to a position overlying said post projection station.
 16. Aslide projector for projecting slides one at a time from a stack ofhorizontally oriented slides and for permitting projection of a slidethat comprises: an entry station including means for receiving a stackof horizontally oriented slides and means for positioning the lowermostslide in said stack at an upper level; a projection station includingmeans for projecting a horizontally oriented slide; an exit stationincluding means for receiving a projected slide at a lower level; saidstations being equi-spaced from an axis; a carrier rotatable in forwardand reverse directions about said axis including means for engagingslides when said carrier is rotated in either direction to move saidslides between said stations; and transport surfaces underlying saidcarrier for supporting slides as they are moved by said carrierincluding a first position that communicates with one side of said entrystation at said upper level, passes through said projection station andterminates in said exit station at said lower level and a second portionthat communicates with the other side of said entry station at saidfirst level.
 17. A slide projector capable of reprojecting a slide afterit has been projected and a second slide has been cycled into aprojection position that comprises: a projection station including meansfor projecting a horizontally oriented slide and means for supporting ahorizontally oriented slide at a first level; and an exit station spacedfrom said projection station including means for removing a slide at asecond level from the transport means of said projector; said transportmeans including a transport surface extending along a curved travel pathfrom said first level at said projection station to said second level atsaid exit station and motive means for moving slides along saidtransport surface, whereby a slide positioned between said projectionstation and said exit station may be reprojected by reversing saidmotive means.
 18. In a slide projector the combination comprising: anentry station including means for supporting a stack of horizontallyoriented slides at an upper level; a projection station; an exit stationincluding a chamber having an open end disposed at a lower level forreceiving projected slides; and transport means for transporting slidesone at a time along a curved travel path from said upper level at saidentry station to said open end of said chamber.